What was found
AIR TURNBACK DUE TO NR 2 ADC FAIL, IAS FLAG, OVERSPEED WARNING, MACH TRIM FAIL, AND PRIMARY PITCH TRIM FAIL. DECLARED AN EMERGENCY AND AIRCRAFT LANDED WITHOUT INCIDENT. PERFORMED PITOT SYSTEM INSTRUMENT TEST, STATIC SYSTEM INSTRUMENT TEST, FUNCTIONAL TEST OF THE AIR DATA SYSTEM STEPS 1 TO 16, AND PRIMARY/SECONDARY ADS ACCURACY TEST. COULD NOT DUPLICATE THIS DISCREPENCY.